1. Field
Aspects of the present invention relates to two wheel drive bicycles, and more particularly, a dual chain-and-sprocket drive mechanism driven by a two-sided paddle-sprocket system.
2. Description of the Related Art
A conventional bicycle includes a frame having a normally non-driven front wheel and a rear driven wheel rotatably mounted thereon. The rear wheel conventionally has a driven element thereon which may comprise a rear chain driven sprocket cluster having several different size gears and a rear derailleur mechanism. A pedal driven crankset, that includes a pedal sprocket or sprockets, is mounted on the frame and serves as a prime mover for the drive wheel. A drive chain is trained around one of the pedal sprockets and one of the sprockets of the rear sprocket cluster. The rear derailleur mechanism is manually operable to shift the drive chain to train it about any desired one of the sprockets of the rear sprocket cluster. If the crank set includes two or three pedal sprockets, a front derailleur mechanism is also mounted to shift the chain to train it about any desired one of the pedal gears. Such shifting of the drive chain allows the operator to select an optimum sprocket ratio for driving the bicycle over the terrain on which it is being ridden. These sprocket ratios are commonly referred to as “speeds”. A rear wheel drive bicycle may have rear wheel and pedal sprocket clusters that provide a large number of speeds with 10, 18 and 21 speed bicycles being in widespread use. The frame also includes a seat for supporting the bicycle rider and a front steerably mounted fork on which the front wheel is rotatably mounted. Handle bars are connected to the front steerable fork for steering the bicycle in known manner. The rear and front derailleurs each have controls mounted on the frame in a position to be conveniently reached by the operator to shift speeds while pedaling the bicycle.
Bicycles are increasingly being ridden off of paved roads and on rough terrain, which is steep, unpaved, frequently wet or muddy and covered by vegetation in places. Off road trails are particularly prone to have treacherously slippery sections caused by mud or uncut vegetation such as grass and weeds. Because of the rough and slippery terrain bikes are driven over, increased traction is desired. To achieve such traction, it is known to provide a multi-speed bicycle with a drive mechanism that allows for simultaneous and constant driving of both the front and rear wheels. This type of drive mechanism will be referred to as a constant dual wheel drive.
Bicycles have traditionally operated as a single-wheel-drive vehicle. As is evidenced by their popularity, single-wheel-drive bicycles are suitable in most cases. Because they only employ single-wheel drive, however, the use of bicycles are, for the most part, somewhat limited to prepared surfaces such as paved streets, sidewalks, and groomed paths. Although just about everyone who has ever ridden a bicycle has ridden on gravel or unprepared surfaces, all riders know that it is more difficult to ride on these types of surfaces due to the fact that drive is being generated by only the rear wheel.
In any event, single-wheel-drive bicycles are the norm because of difficulties involved in transferring to the front wheel the drive generated by the rider. The difficulty in generating drive via the front wheel of a bicycle results from the need to allow the fork (on which the front wheel is mounted) freedom to turn substantially in either direction from the center position in order to permit the cyclist to steer the bicycle. Because the fork must be free to turn, it is not possible to directly connect the pedals to the front wheel.
As off road biking has gained broader appeal, the demands that riders place on their bicycles have increased dramatically. Downhill, snow, and endurance races demand the increased traction and mobility of a two wheel drive bicycle system. Conventional bicycles are powered through a chain linking the pedal crankshaft to the rear wheel. Bicyclists are now facing many obstacles where having only rear wheel drive can lead to bicycle damage or personal injury. For professional riders, precious race time is lost avoiding obstacles such as logs, rocks, loose sand, mud, or ice. Traction and climbing ability are severely limited in extreme mountain conditions by only having the rear wheel provide power. In fact, biking professionals teach that only through learning to keep your weight on the rear wheel will beginners ever hope to improve their off-road skills. Accordingly, there is a need in the industry for a two wheeled drive bicycle which efficiently transfers power from the pedals to the front wheels, provides the rider with increased ability to safely negotiate rough terrain, and which does not detract from the aesthetic qualities and appearances of the bicycle structure itself.
The concept of a two wheel drive bicycle is not a new one. Several two wheel drive bicycle systems are patented at present using various combinations of chains, flexible cable shafts, and rocker arms mounted on the handlebars to transfer power either directly from the pedals to the front wheel or from the rear wheel to the front wheel. While two-wheel-drive bicycles have been proposed, there remains a need for an easily-operable and readily steerable two-wheel-drive bicycle, so that riders will have greater opportunity for enjoyable cycling on off-road trails and other unprepared surfaces.
Therefore, a two-wheel-drive bicycle overcoming various problems and shortcomings of the prior art would be an important improvement in the art.